Rice – the ingredient that makes a Spanish paella so particular

Penelope Casas' The Foods and Wines of Spain explains that

Paella is a word that has come worldwide to mean a Spanish rice dish with a variety of seafood and usually some chicken. However, the word originally referred only to the pan in which the food was cooked--the paella or paellera, from the Latin word for pan, patella. Paellas actually come in endless varieties, depending on the chef and on regional specialties.

She emphasizes the technique more than traditional ingredients (which she notes that no two Spaniards will agree on), but includes recipes for a number of different rice dishes from many regions, all prepared in basically the same manner.

Interestingly, her Paella a la Valenciana (Tradicional) actually doesn't call for saffron (it does call for paprika). The meats are snails and rabbit, and she does call for an onion, but it's only used to steep for a while in the broth, and later discarded. She includes a single tomato which is cooked down with green peppers and garlic. Most of her other paella recipes include onion in this step, but it is notably absent from this recipe. She also calls for lima beans and "wide, flat string beans", and serve the dish with scallions on the side.

'Paella rice' is not actually a variety of rice, but a category suitable, as the its name suggests, for making paella. Some common varieties are: Bahia, Balilla, Bomba, Senia, and Calasparra; the particular variety should be indicated on the packet that you choose.

These varieties differ from risotto rices, such as arborio and carnaroli, in not creating a creamy 'sauce' around the rice. Paella rice should stick together, but be distinct and not in a creamy 'sauce'.

Arborio rice has a creamy, chewy texture due to its higher amylopectin (one of two components in its starch) content. Paella rice absorbs more liquid than risotto rices, however it too would become 'creamy' if you stirred it like a risotto, since it also has a high starch content.